The invention relates to a coffee-bean roaster for small quantities, with a vertically directed cylindrical roasting chamber, a fan for supplying air to the roasting chamber for the swirling of coffee beans introduced into the roasting chamber, a suction port for sucking up supply air, an exhaust-air port which is preceded by a separator device for coffee-bean residues transported together with the exhaust air, and a heating device in the supply-air conduit.
In order to develop the flavorings and aromatics in green coffee beans, it is necessary to roast these before they can be brewed with hot water for coffeemaking. The quality of the finished coffee is essentially determined by the chosen length of time between roasting and the making of the coffee drink. It is therefore desirable to carry out the roasting operation only immediately before the coffee is delivered to the final consumer.
Automatic roasters intended for small quantities of, for example, 250-1,000 g have already become known for this purpose. It is thus possible, on the one hand, also to use these automatic roasting machines in the retail trade and, on the other hand, to be able to offer the customer different coffee mixtures on request.
German Patent Specification No. 2,531,390 makes known a coffee-bean roaster, in which there is a roasting chamber enclosed by a housing and having a perforated bottom, through which heated roasting air is blown into the roasting chamber from below by a fan, so that the beans present in the roasting chamber are swirled round by rising along one wall and falling down again on the opposite wall. This cylindrical swirling of the green coffee beans to be roasted ensures that all the coffee beans are roasted uniformly and from all sides.
In order to cool the roasted coffee beans, in this apparatus there is an additional fan which swirls the coffee beans with ambient air and thereby cools them. The applicance involves a very high outlay in terms of construction and is therefore uneconomic for relatively small roasting quantities.
WO No. 84/01271 makes known another coffee-bean roaster having, underneath a supply-air plenum, a cylindrical roasting chamber in which a toroidal movement is imparted to the introduced coffee beans by means of an air jet blowing into the roasting chamber from a blowing-in pipe arranged coaxially relative to the roasting chamber. The air stream for roasting the coffee beans is generated by a first fan. A second fan serves for cooling the roasted coffee beans. This apparatus likewise involves a very high outlay in terms of construction, with the result that the roasting of relatively small quantities usually entails substantially higher costs than factory roasting.
Finally, a coffee-bean roaster for small quantities has become known from German Offenlegunsschrift No. 3,217,055, and in this the coffee beans are swirled up through a sieve from below and, after roasting, as a result of the opening of a flap pass out of the roasting chamber onto a grid for cooling. They are thus cooled by the supply air to the roasting chamber, with the heating switched off. This apparatus makes it possible to roast only very small quantities of coffee for domestic use. Because of the simple design, there is no guarantee of uniformity of the roasting process and roasting result.
Starting from WO No. 84,01271, the object on which the invention is based is to provide a simplified coffeebean roaster which requires only a single fan for roasting and cooling the coffee beans and is of simple constructional design, but in which the roasting process gives a uniform roasting result, and which can be controlled in a flexible way.
This object is achieved by means of the invention indicated in the claims. Advantageous developments of the invention are given in subclaims.
The coffee-bean roaster according to the invention is, in principle, designed in such a way that the supply air is introduced into the roasting chamber from above via several inlet conduits and is eliminated again coaxially upwards.
For this purpose, the coffee-bean roaster has a vertically directed cylindrical roasting chamber which is designed so that the hot air blown into the roasting chamber from above is supplied off-center via at least two blowing-in conduits which are directed towards the bottom of the roasting chamber and of which the blowing-out direction relative to the roasting-chamber axis is set at a respective equidirectional oblique blowing-out angle of between 0.degree. up to and 30.degree. in the tangential direction of the roasting chamber.
The coffee beans are introduced into the roasting chamber above the latter through a coffee-bean inlet which can be shut off. On the underside of the roasting chamber there is an openable bottom, through which the roasted coffee beans can fall out of the roasting chamber into a collecting container which is arranged underneath it and the air-permeable bottom of which at the same time forms the suction port for sucking up the supply air.
This arrangement according to the invention avoids the need for an additional fan for the cooling operation. The already roasted coffee beans can thus be cooled directly by the suction air of the supply-air conduit. It is also possible, even while one batch of coffee is being cooled, to roast the next batch.
The coffee-bean roaster according to the invention is of simple design. Only simple control and switching devices, actuable manually or by means of an automatic programmer, for shutting off the coffee-bean inlet, for opening the bottom of the roasting chamber and for controlling the air supply, temperature and roasting or cooling time are required. The apparatus according to the invention can be designed as a table-top unit, but at the same time it is possible to roast a batch of coffee of a quantity of approximately 500-600 g within a very short time.
The invention is explained in more detail below with reference to an exemplary embodiment.